How to combine multiple internet connections to increase performance.

I have a laptop with a fairly typical network setup. One wired connection one 802.11n card and an AT&T WWAN card. With the WWAN i typically get speeds of about 3Mbit (but varries) and depending on where i connect i get etween 1.5Mbit and 8Mbit through the wireless (connecting to a wireless network with DSL or cable usually). I rarely use the wired connection. For easy numbers lets assume I'm at my house with 3Mbit WWAN connection and 3Mbit WAN connection. The WWAN showes up similer to a dial up connection in my connections window. the WAN as standard wireless. I run Windows Vista. I can connect to the internet with either connection or connect them both at once. I havent done much testing yet so when both are connected i'm not sure if it's using WWAN, WAN or both. I want to make the best- fastest connection possible. Will windows automatically split connections between them? Do I need to bridge them for that? I want to et my WWAN card to auto connect so when ever i open my laptop i get WWAN and if available and I connect to a WAP get an aditional speed boost. Do I need 3rd party tools etc to do this? I don't necessary need a single 6Mbit connection some sort of load ballancing would be ok to as i'm often doing multiple things. I just want to make sure the fastest connection is always used because sometimes WWAN is faster and others WAN is faster but ideally i'd just like to combine them.